A. Field of the Invention
The present invention relates generally to electronic communications and, more particularly, to packet loss concealment in packet switching communications networks.
B. Description of the Related Art
Today, real-time telecommunication signals (e.g., voice, video, audio, data, and multimedia) are increasingly transported via packet switching networks. For example, Internet applications now routinely packetize voice, video, and audio signals and periodically transmit, or stream, the resulting data packets from source to destination. However, when such packetized streams traverse a packet switching network such as the Internet, some of the transmitted packets may be corrupted or lost. For example, packets are sometimes corrupted through bit errors in transmission and packets are sometimes dropped or discarded due to traffic congestion at buffer pools in network switches or routers. Such corrupted and dropped packets constitute loss of information and thus degrade the quality of transmitted signals as perceived by end users.
To improve quality of reception and perception, various error correction and packet loss concealment schemes have been devised. Whereas error correction techniques attempt to fix bit errors or bit erasures in a received signal, packet loss concealment techniques attempt to mask or camouflage missing packets in a received signal by generating and substituting replacement packets when the signal is presented to the end user at the signal destination. Basic packet loss concealment methods simply attempt to replace missing information with information from previous packets, while more sophisticated loss concealment methods synthesize replacement information based on previously received information and/or knowledge of the signal source.
Generally, known loss concealment methods provide acceptable levels of perceptual quality (e.g., toll quality for signals transmitted by commercial providers for paying customers) when packet losses are relatively few and far between. However, when packet loss rates increase (e.g., due to network congestion and/or channel degradation), or when bursts of consecutive packet loss occur, known loss concealment methods can fail to provide acceptable signal quality.
Consequently, a need exists for improved forms of packet loss concealment.